RESUMEN
OBJECTIVES: To assess the clinical usefulness of bone-specific alkaline phosphatase (B-AKP) to detect or rule out bone metastases in patients with prostate cancer. METHODS: Between November 2001 and July 2003 111 patients with the diagnosis of prostate adenocarcinoma were evaluated to rule out bone metastases. Bone metastases were studied after clinical suspicion, PSA value higher than 10 ng/ml, or Gleason score higher than 7. Bone scan was used as detection test. Patients were tested for serum B-AKP with a reference value equal or higher than 30ng/ml. The sensitivity, specificity, positive predictive value and negative predictive value of B-AKP were measured in comparison to bone scan as the gold standard. RESULTS: 111 patients with the diagnosis of prostate adenocarcinoma were evaluated to rule out bone metastases. Mean age was 69.70 years (50-83 years). Average B-AKP value was 29.28 ng/ml (9-56 ng/ml). Bone scan was positive in 31 patients. Among these 31, 26 patients had positive B-AKP and five negative. AP patients had negative bone scan. From this AP patients, B-AKP was positive in 17 and negative in 63. The sensitivity of the test was 83.8%. The specificity was 78%. Positive predictive value was 60% and negative predictive value was 92%. CONCLUSIONS: Bone alkaline phosphatase is a greatly useful test for the study of patients with prostate cancer in whom bone metastases are suspected either to confirm them or to rule out their presence.